278 Stewardship of energy use by beef cows: maintenance requirements of the U.S. cowherd.

Maintenance energy requirements have been reported to account for about 71% of the total dietary energy expenditure in beef production. Furthermore, about 70% of dietary maintenance energy used in beef production is required for the cow herd. Therefore, a staggering 50% of the total energy expended in producing beef is used for maintenance of the cow. However, little work has been conducted since the 1980’s to determine if this important driver of beef production sustainability has changed over time. Adoption of improved management and genetic selection for growth and increased carcass weight has led to improved post-weaning performance. For example, finished cattle carcass weights continue to increase in a linear fashion at the rate of about 2.7 kg per yr. This has led to increased beef production per cow; in fact, the industry produced 14% more beef in 2017 with 1.8 million fewer cows compared to 1992. However, data from several sources indicate that commercial cow/calf environment and management systems restrict the capability of modern cattle to express their genetic potential during the pre-weaning phase. Notable restrictions are reproductive efficiency and weaning weights. Recent Kansas Farm Management enterprise analyses indicate that both production (weight) and price impact profit, although they are much less important in explaining differences in ranch profitability than costs. In fact, the most profitable operations had $114 per cow/calf unit lower feed and pasture cost compared to low profit operations. Aggressive genetic selection for growth, gradual increases in mature size and relatively high capacity for milk production in modern beef cattle could result in a cow herd with increased maintenance energy requirements, increased appetite, and overall, increased annual carrying costs over time.